JP2022062902A - Vacuum pump and rotary cylindrical body included in the same - Google Patents

Abstract

To provide a vacuum pump which enables reduction of stress without decreasing the number of rotation of a rotary cylindrical body (a rotating body) and improvement of exhaust performance, and to provide the rotary cylindrical body included in the vacuum pump.SOLUTION: At an exhaust port side lower part of a cylindrical part (a rotary cylindrical body) included in a vacuum pump, an extension part extending to the downstream side relative to a fixing side component of a screw groove exhaust element is provided. At the extension part, stress which is generated at the inner diameter side during rotation gets smaller as the outer diameter gets smaller. Thus, a structure having a diameter reduction part enables reduction of the stress which is generated at the inner diameter side of the cylindrical part without decreasing the number of rotation of a rotating body (such as the cylindrical part). Further, a moderately diameter reducing structure is adopted at the extension part to reduce stress concentration in the diameter reduction part.SELECTED DRAWING: Figure 5

Description

The present invention relates to a vacuum pump and a rotating cylinder provided in the vacuum pump.
More specifically, the present invention relates to a vacuum pump that reduces the stress applied to the rotating cylinder, and a rotating cylinder provided in the vacuum pump.

Some vacuum pumps for performing vacuum exhaust processing in the arranged vacuum chamber are provided with a rotating body and a thread groove exhaust element (thread groove type exhaust mechanism / thread groove pump portion). The vacuum pump provided with the threaded groove exhaust element is provided with a rotating cylinder (rotor cylindrical portion) without a rotating blade on the lower side of the rotating body on which the rotating blade is arranged, and compresses the gas in the threaded groove exhaust element. It is configured to be used.
In general, in a vacuum pump including a vacuum pump provided with such a rotor cylindrical portion, a stress is generated on the inner diameter side of the rotor cylindrical portion due to centrifugal force, and the stress may exceed the design standard value.
FIG. 9 is a diagram for explaining the conventional turbo molecular pump 100.
As shown in FIG. 9, in the conventional turbo molecular pump 100, a cylindrical portion 102d is disposed so as to face axially with a threaded spacer 131 via a gap (clearance). When stress is generated in the cylindrical portion 102d, a creep phenomenon occurs in which the cylindrical portion 102d is gradually deformed and expanded due to long-term motion at a high temperature.
The creep life, which is the period until the specified value of the clearance between the threaded spacer 131 and the cylindrical portion 102d becomes smaller due to this creep phenomenon, should be as long as possible from the viewpoint of maintenance cost.

Japanese Patent Application Laid-Open No. 10-246197

In Patent Document 1, the outer diameters of the rotor blades are set to the exhaust port side and the intake port side for the purpose of preventing local stress and temperature rise in the rotor blade and the portion supporting the rotary blade even when the rotor is rotated at high speed. It describes the technology to make it different in.

Further, in addition to the configuration as described in Patent Document 1 described above, the stress is reduced by lowering the number of rotations of the rotating body (rotor blade / rotating cylinder).
However, if the rotation speed of the rotating body is lowered, the exhaust performance is lowered.

It is an object of the present invention to provide a vacuum pump capable of reducing stress without lowering the rotation speed of the rotating cylinder (rotating body) and improving exhaust performance, and a rotating cylinder provided in the vacuum pump. And.

According to the first aspect of the present invention, an exterior body in which an intake port and an exhaust port are formed, a screw groove type exhaust mechanism fixed to the exterior body and having a thread groove, and a thread groove type exhaust mechanism contained in the exterior body and rotatably formed. It has a supported rotating shaft, a facing portion that is disposed on the rotating shaft and faces the threaded groove type exhaust mechanism via a gap, and an extended portion that extends downstream from the threaded groove type exhaust mechanism. Provided is a vacuum pump comprising: a reduced diameter portion having an outer diameter smaller than the outer diameter of the facing portion in the stretched portion, and a rotating cylindrical body having a slow-reduced diameter structure for reducing stress concentration. do.
The invention of the present application according to claim 2 provides the vacuum pump according to claim 1, wherein the slow-reducing diameter structure is a tapered structure.
According to the third aspect of the present invention, there is provided the vacuum pump according to the first aspect, wherein the slow-reducing diameter structure has a curved surface shape.
In the invention of the present application according to claim 4, the vacuum pump according to any one of claims 1 to 3, wherein the slow-reduced diameter structure is included in the reduced-diameter portion.
According to the fifth aspect of the present invention, an exterior body in which an intake port and an exhaust port are formed, a threaded groove type exhaust mechanism fixed to the exterior body and having a thread groove, and a thread groove type exhaust mechanism contained in the exterior body so as to be rotatable. A rotating cylinder of a vacuum pump provided with a supported rotating shaft, which is arranged on the rotating shaft and faces the threaded groove type exhaust mechanism via a gap and from the threaded groove type exhaust mechanism. Also characterized by having a stretched portion extended to the downstream side, a reduced diameter portion having an outer diameter smaller than the outer diameter of the facing portion in the stretched portion, and a slow-reduced diameter structure for reducing stress concentration. A rotating cylinder is provided.

According to the present invention, the stress of the portion of the rotating cylinder due to the creep life can be reduced without lowering the rotation speed. Performance can be maintained or improved.

It is a figure which showed the schematic structural example of the turbo molecular pump which concerns on embodiment of this invention. It is a figure which showed the circuit diagram of the amplifier circuit used in embodiment of this invention. It is a time chart which shows the control when the current command value is larger than the detected value in embodiment of this invention. It is a time chart which shows the control when the current command value is smaller than the detected value in embodiment of this invention. It is a figure which showed the schematic structural example of the turbo molecular pump which concerns on 1st Embodiment of this invention. It is a figure for demonstrating the cylindrical part and the extension part of the turbo molecular pump which concerns on 1st Embodiment of this invention. It is an enlarged view of the cylindrical part and the stretched part shown in FIG. It is a figure for demonstrating the shape of the stretched portion. It is a figure which showed the schematic structure example of the conventional turbo molecular pump.

(I) Outline of the Embodiment In the turbo molecular pump (vacuum pump) according to the embodiment of the present invention, the fixed side component of the thread groove exhaust element in the lower part of the exhaust port side of the cylindrical portion (rotary cylindrical body) provided in the turbo molecular pump. A stretched portion is provided, which is stretched to the downstream side of the section. Then, a reduced diameter portion is provided in the stretched portion.
More specifically, the lower end portion (exhaust port side end portion) of the cylindrical portion is designed to be longer than the thread groove exhaust element, and the extension portion is provided. Then, a reduced diameter portion having a smaller outer diameter than the portion (opposing portion) on the intake port side of the rotor cylindrical portion and facing the thread groove exhaust element is provided in the extended portion of the rotor cylindrical portion. Further, a slow-reduced diameter structure is adopted for the stretched portion. This slowly reduced diameter structure means a structure in which the diameter is gradually reduced.

In the stretched portion, the stress generated on the inner diameter side during rotation becomes smaller as the outer diameter becomes smaller. At least, the stress generated on the inner diameter side of the cylindrical portion can be reduced.

(Ii) Details of Embodiments Hereinafter, preferred embodiments of the present invention will be described in detail with reference to FIGS. 1 to 8.
A vertical sectional view of the turbo molecular pump 100 is shown in FIG. In FIG. 1, in the turbo molecular pump 100, an intake port 101 is formed at the upper end of a cylindrical outer cylinder 127. A rotating body 103 in which a plurality of rotary blades 102 (102a, 102b, 102c ...), Which are turbine blades for sucking and exhausting gas, are radially and multistagely formed on the peripheral portion inside the outer cylinder 127. Is provided. A rotor shaft 113 is attached to the center of the rotating body 103, and the rotor shaft 113 is floated and supported and position-controlled in the air by, for example, a 5-axis controlled magnetic bearing.

In the upper radial electromagnet 104, four electromagnets are arranged in pairs on the X-axis and the Y-axis. Four upper radial sensors 107 are provided in the vicinity of the upper radial electromagnet 104 and corresponding to each of the upper radial electromagnets 104. As the upper radial sensor 107, for example, an inductance sensor having a conduction winding, an eddy current sensor, or the like is used, and the position of the rotor shaft 113 is based on the change in the inductance of the conduction winding that changes according to the position of the rotor shaft 113. Is detected. The upper radial sensor 107 is configured to detect the radial displacement of the rotor shaft 113, that is, the rotating body 103 fixed to the rotor shaft 113, and send it to the control device 200.

In this control device 200, for example, a compensator circuit having a PID adjustment function generates an excitation control command signal of the upper radial electromagnet 104 based on a position signal detected by the upper radial sensor 107, and is shown in FIG. The amplifier circuit 150 (described later) excites and controls the upper radial electromagnet 104 based on the excitation control command signal, so that the upper radial position of the rotor shaft 113 is adjusted.

The rotor shaft 113 is formed of a high magnetic permeability material (iron, stainless steel, etc.) and is attracted by the magnetic force of the upper radial electromagnet 104. Such adjustment is performed independently in the X-axis direction and the Y-axis direction, respectively. Further, the lower radial electric magnet 105 and the lower radial sensor 108 are arranged in the same manner as the upper radial electric magnet 104 and the upper radial sensor 107, and the lower radial position of the rotor shaft 113 is set to the upper radial position. It is adjusted in the same way as.

Further, the axial electromagnets 106A and 106B are arranged so as to vertically sandwich the disk-shaped metal disk 111 provided in the lower part of the rotor shaft 113. The metal disk 111 is made of a high magnetic permeability material such as iron. An axial sensor 109 is provided to detect the axial displacement of the rotor shaft 113, and the axial position signal thereof is configured to be sent to the control device 200.

Then, in the control device 200, for example, a compensation circuit having a PID adjustment function sends an excitation control command signal for each of the axial electromagnet 106A and the axial electromagnet 106B based on the axial position signal detected by the axial sensor 109. The generated amplifier circuit 150 excites and controls the axial electromagnet 106A and the axial electromagnet 106B based on these excitation control command signals, so that the axial electromagnet 106A attracts the metal disk 111 upward by magnetic force. , The axial electromagnet 106B attracts the metal disk 111 downward, and the axial position of the rotor shaft 113 is adjusted.

As described above, the control device 200 appropriately adjusts the magnetic force exerted by the axial electromagnets 106A and 106B on the metal disk 111, magnetically levitates the rotor shaft 113 in the axial direction, and holds the rotor shaft 113 in the space in a non-contact manner. ing. The amplifier circuit 150 that excites and controls the upper radial electromagnet 104, the lower radial electromagnet 105, and the axial electromagnets 106A and 106B will be described later.

On the other hand, the motor 121 includes a plurality of magnetic poles arranged in a circumferential shape so as to surround the rotor shaft 113. Each magnetic pole is controlled by the control device 200 so as to rotationally drive the rotor shaft 113 via an electromagnetic force acting on the rotor shaft 113. Further, the motor 121 incorporates a rotation speed sensor such as a Hall element, a resolver, an encoder, etc. (not shown), and the rotation speed of the rotor shaft 113 is detected by the detection signal of the rotation speed sensor.

Further, for example, a phase sensor (not shown) is attached in the vicinity of the lower radial sensor 108 to detect the phase of rotation of the rotor shaft 113. The control device 200 detects the position of the magnetic pole by using both the detection signals of the phase sensor and the rotation speed sensor.

A plurality of fixed wings 123 (123a, 123b, 123c ...) Are arranged with the rotary blades 102 (102a, 102b, 102c ...) Separated from a slight gap. The rotary blades 102 (102a, 102b, 102c ...) Are formed so as to be inclined by a predetermined angle from a plane perpendicular to the axis of the rotor shaft 113 in order to transfer exhaust gas molecules downward by collision. There is.

Similarly, the fixed blade 123 is also formed so as to be inclined by a predetermined angle from a plane perpendicular to the axis of the rotor shaft 113, and is arranged alternately with the steps of the rotary blade 102 toward the inside of the outer cylinder 127. ing. The outer peripheral end of the fixed wing 123 is supported in a state of being fitted between a plurality of stacked fixed wing spacers 125 (125a, 125b, 125c ...).

The fixed wing spacer 125 is a ring-shaped member, and is made of, for example, a metal such as aluminum, iron, stainless steel, or copper, or a metal such as an alloy containing these metals as a component. An outer cylinder 127 is fixed to the outer periphery of the fixed wing spacer 125 with a slight gap. A base portion 129 is arranged at the bottom of the outer cylinder 127. An exhaust port 133 is formed in the base portion 129 and communicates with the outside. The exhaust gas that has entered the intake port 101 from the chamber side and has been transferred to the base portion 129 is sent to the exhaust port 133.

Further, depending on the application of the turbo molecular pump 100, a threaded spacer 131 is arranged between the lower portion of the fixed wing spacer 125 and the base portion 129. The threaded spacer 131 is a cylindrical member made of a metal such as aluminum, copper, stainless steel, iron, or an alloy containing these metals as a component, and has a plurality of spiral thread grooves 131a on the inner peripheral surface thereof. It is engraved. The direction of the spiral of the thread groove 131a is the direction in which the molecules of the exhaust gas are transferred toward the exhaust port 133 when the molecules of the exhaust gas move in the rotation direction of the rotating body 103. A cylindrical portion 102d is hung at the lowermost portion of the rotating body 103 following the rotary blades 102 (102a, 102b, 102c ...). The outer peripheral surface of the cylindrical portion 102d is cylindrical and projects toward the inner peripheral surface of the threaded spacer 131, and is brought close to the inner peripheral surface of the threaded spacer 131 with a predetermined gap. There is. The exhaust gas transferred to the screw groove 131a by the rotary blade 102 and the fixed blade 123 is sent to the base portion 129 while being guided by the screw groove 131a.

The base portion 129 is a disk-shaped member constituting the base portion of the turbo molecular pump 100, and is generally made of a metal such as iron, aluminum, or stainless steel. Since the base portion 129 physically holds the turbo molecular pump 100 and also has the function of a heat conduction path, a metal having rigidity such as iron, aluminum or copper and having high thermal conductivity is used. Is desirable.

In such a configuration, when the rotary blade 102 is rotationally driven by the motor 121 together with the rotor shaft 113, exhaust gas is taken in from the chamber through the intake port 101 by the action of the rotary blade 102 and the fixed blade 123. The exhaust gas taken in from the intake port 101 passes between the rotary blade 102 and the fixed blade 123, and is transferred to the base portion 129. At this time, the temperature of the rotary blade 102 rises due to frictional heat generated when the exhaust gas comes into contact with the rotary blade 102, conduction of heat generated by the motor 121, etc., but this heat is radiation or gas of the exhaust gas. It is transmitted to the fixed wing 123 side by conduction by molecules or the like.

The fixed wing spacers 125 are joined to each other at the outer peripheral portion, and transfer heat received by the fixed wing 123 from the rotary wing 102, frictional heat generated when exhaust gas comes into contact with the fixed wing 123, and the like to the outside.

In the above description, it is assumed that the threaded spacer 131 is arranged on the outer periphery of the cylindrical portion 102d of the rotating body 103, and the screw groove 131a is engraved on the inner peripheral surface of the threaded spacer 131. However, on the contrary, there is a case where a screw groove is carved on the outer peripheral surface of the cylindrical portion 102d, and a spacer having a cylindrical inner peripheral surface is arranged around the thread groove.

Further, depending on the application of the turbo molecular pump 100, the gas sucked from the intake port 101 is the upper radial electromagnet 104, the upper radial sensor 107, the motor 121, the lower radial electromagnet 105, the lower radial sensor 108, and the shaft. The circumference of the electrical component is covered with a stator column 122 so that it does not invade the electrical component composed of the directional electromagnets 106A, 106B, the axial sensor 109, etc., and the inside of the stator column 122 is kept at a predetermined pressure by a purge gas. It may hang down.

In this case, a pipe (not shown) is arranged in the base portion 129, and purge gas is introduced through this pipe. The introduced purge gas is sent to the exhaust port 133 through the gaps between the protective bearing 120 and the rotor shaft 113, between the rotor and the stator of the motor 121, and between the stator column 122 and the inner peripheral side cylindrical portion of the rotary blade 102.

Here, the turbo molecular pump 100 requires identification of a model and control based on individually adjusted unique parameters (for example, various characteristics corresponding to the model). In order to store this control parameter, the turbo molecular pump 100 includes an electronic circuit unit 141 in its main body. The electronic circuit unit 141 is composed of a semiconductor memory such as EEP-ROM, electronic components such as semiconductor elements for accessing the semiconductor memory, and a substrate 143 for mounting them. The electronic circuit portion 141 is housed in a lower portion of a rotational speed sensor (not shown) near the center of a base portion 129 constituting the lower portion of the turbo molecular pump 100, and is closed by an airtight bottom lid 145.

By the way, in the semiconductor manufacturing process, some of the process gases introduced into the chamber have the property of becoming solid when the pressure becomes higher than the predetermined value or the temperature becomes lower than the predetermined value. be. Inside the turbo molecular pump 100, the pressure of the exhaust gas is the lowest at the intake port 101 and the highest at the exhaust port 133. If the pressure rises above a predetermined value or the temperature drops below a predetermined value while the process gas is being transferred from the intake port 101 to the exhaust port 133, the process gas becomes a solid state and becomes a turbo molecule. It adheres to the inside of the pump 100 and accumulates.

For example, when SiCl ₄ is used as a process gas in an Al etching apparatus, it is a solid product (for example, at a low vacuum (760 [torr] to ^10-2 [torr]) and at a low temperature (about 20 [° C.]). It can be seen from the vapor pressure curve that AlCl ₃ ) is deposited and adheres to the inside of the turbo molecular pump 100. As a result, when a deposit of process gas is deposited inside the turbo molecular pump 100, this deposit narrows the pump flow path and causes the performance of the turbo molecular pump 100 to deteriorate. The above-mentioned product was in a state of being easily solidified and adhered in a high pressure portion near the exhaust port 133 and the screwed spacer 131.

Therefore, in order to solve this problem, conventionally, a heater or an annular water cooling tube 149 (not shown) is wound around the outer periphery of the base portion 129 or the like, and a temperature sensor (for example, a thermistor) (for example, not shown) is embedded in the base portion 129, for example. Based on the signal of this temperature sensor, the heating of the heater and the control of cooling by the water cooling tube 149 (hereinafter referred to as TMS; Temperature Management System) are performed so as to keep the temperature of the base portion 129 at a constant high temperature (set temperature). It has been.

Next, with respect to the turbo molecular pump 100 configured as described above, an amplifier circuit 150 that excites and controls the upper radial electromagnet 104, the lower radial electromagnet 105, and the axial electromagnets 106A and 106B will be described. The circuit diagram of this amplifier circuit 150 is shown in FIG.

In FIG. 2, one end of the electromagnet winding 151 constituting the upper radial electromagnet 104 and the like is connected to the positive electrode 171a of the power supply 171 via the transistor 161 and the other end thereof is the current detection circuit 181 and the transistor 162. It is connected to the negative electrode 171b of the power supply 171 via. The transistors 161 and 162 are so-called power MOSFETs, and have a structure in which a diode is connected between the source and the drain thereof.

At this time, in the transistor 161 the cathode terminal 161a of the diode is connected to the positive electrode 171a, and the anode terminal 161b is connected to one end of the electromagnet winding 151. Further, in the transistor 162, the cathode terminal 162a of the diode is connected to the current detection circuit 181 and the anode terminal 162b is connected to the negative electrode 171b.

On the other hand, in the current regeneration diode 165, the cathode terminal 165a is connected to one end of the electromagnet winding 151, and the anode terminal 165b is connected to the negative electrode 171b. Similarly, in the current regeneration diode 166, the cathode terminal 166a is connected to the positive electrode 171a, and the anode terminal 166b is connected to the other end of the electromagnet winding 151 via the current detection circuit 181. It has become so. The current detection circuit 181 is composed of, for example, a hall sensor type current sensor or an electric resistance element.

The amplifier circuit 150 configured as described above corresponds to one electromagnet. Therefore, when the magnetic bearing is controlled by 5 axes and there are a total of 10 electromagnets 104, 105, 106A, and 106B, the same amplifier circuit 150 is configured for each of the electromagnets, and 10 amplifier circuits are provided for the power supply 171. 150 are connected in parallel.

Further, the amplifier control circuit 191 is composed of, for example, a digital signal processor unit (hereinafter referred to as a DSP unit) (hereinafter referred to as a DSP unit) of the control device 200, and the amplifier control circuit 191 switches on / off of the transistors 161 and 162. It has become like.

The amplifier control circuit 191 is adapted to compare a current value detected by the current detection circuit 181 (a signal reflecting this current value is referred to as a current detection signal 191c) with a predetermined current command value. Then, based on this comparison result, the magnitude of the pulse width (pulse width time Tp1 and Tp2) generated in the control cycle Ts, which is one cycle by PWM control, is determined. As a result, the gate drive signals 191a and 191b having this pulse width are output from the amplifier control circuit 191 to the gate terminals of the transistors 161 and 162.

It is necessary to control the position of the rotating body 103 at high speed and with a strong force when the rotating body 103 passes through the resonance point during the accelerated operation of the rotating speed or when a disturbance occurs during the constant speed operation. .. Therefore, a high voltage of, for example, about 50 V is used as the power supply 171 so that the current flowing through the electromagnet winding 151 can be rapidly increased (or decreased). Further, a normal capacitor is normally connected between the positive electrode 171a and the negative electrode 171b of the power supply 171 for the purpose of stabilizing the power supply 171 (not shown).

In such a configuration, when both the transistors 161 and 162 are turned on, the current flowing through the electromagnet winding 151 (hereinafter referred to as the electromagnet current iL) increases, and when both are turned off, the electromagnet current iL decreases.

Further, when one of the transistors 161 and 162 is turned on and the other is turned off, the so-called flywheel current is maintained. By passing the flywheel current through the amplifier circuit 150 in this way, the hysteresis loss in the amplifier circuit 150 can be reduced, and the power consumption of the entire circuit can be suppressed to a low level. Further, by controlling the transistors 161 and 162 in this way, it is possible to reduce high frequency noise such as harmonics generated in the turbo molecular pump 100. Further, by measuring this flywheel current with the current detection circuit 181 it becomes possible to detect the electromagnet current iL flowing through the electromagnet winding 151.

That is, when the detected current value is smaller than the current command value, as shown in FIG. 3, the transistors 161 and 162 are used only once in the control cycle Ts (for example, 100 μs) for the time corresponding to the pulse width time Tp1. Turn both on. Therefore, the electromagnet current iL during this period increases from the positive electrode 171a to the negative electrode 171b toward the current value iLmax (not shown) that can be passed through the transistors 161 and 162.

On the other hand, when the detected current value is larger than the current command value, as shown in FIG. 4, both the transistors 161 and 162 are turned off only once in the control cycle Ts for the time corresponding to the pulse width time Tp2. .. Therefore, the electromagnet current iL during this period decreases from the negative electrode 171b to the positive electrode 171a toward the current value iLmin (not shown) that can be regenerated via the diodes 165 and 166.

In either case, after the pulse width times Tp1 and Tp2 have elapsed, either one of the transistors 161 and 162 is turned on. Therefore, during this period, the flywheel current is held in the amplifier circuit 150.

FIG. 5 is a diagram for explaining the outline of the turbo molecular pump 100 according to the first embodiment.
FIG. 6 is a diagram for explaining a facing portion 10t and a stretched portion 11 (slowly reduced diameter structure 11a and reduced diameter portion 50) in the cylindrical portion 102d of the turbo molecular pump 100 shown in FIG.
FIG. 7 is an enlarged view of the opposed portion 10t, the stretched portion 11, the loosely reduced diameter structure 11a, and the reduced diameter portion 50 in the cylindrical portion 102d.
As shown in FIGS. 5 to 7, the cylindrical portion 102d is a stretched portion extending toward the exhaust port 133 from the threaded spacer 131 and the facing portion 10t facing the threaded spacer 131 in the axial direction with a predetermined gap. It has a portion 11, a slow-reduced diameter structure 11a, and a reduced-diameter portion 50. The shape of the reduced diameter portion 50 is cylindrical like the cylindrical portion 102d.
As is clear from FIG. 6, the stretched portion 11 is composed of a slow-reduced diameter structure 11a and a reduced-diameter portion 50.

Further, in the present embodiment, the inner diameter of the facing portion 10t in the cylindrical portion 102d will be described as r, and the outer diameter will be described as Rt.
Then, as shown in FIG. 7, the outer diameter of the lower end portion (exhaust port 133 side) and the reduced diameter portion 50 of the slow-reduced diameter structure 11a will be described as Rs, and the gradual outer diameter of the slow-reduced diameter structure 11a will be described as m. .. In this embodiment, "gradual outer diameter" is used to mean "outer diameter that changes little by little".
The cylindrical portion 102d provided in the turbo molecular pump 100 according to the present embodiment is the cylindrical portion 102d (opposing portion 10t) of the portion not the stretched portion 11 in the stretched portion 11 stretched toward the exhaust port 133 side from the threaded spacer 131. A slow-reduced diameter structure 11a having a gradual outer diameter m smaller than the outer diameter Rt is formed. In the embodiment shown in FIGS. 5 to 7, the value of the gradual outer diameter m gradually decreases from the intake port side to the exhaust port side (that is, the outer diameter gradually changes).

In other words, the cylindrical portion 102d according to the present embodiment has a portion (relaxed diameter structure 11a) having a gradient of a predetermined angle θ on the outer diameter side of the stretched portion 11. This gradient can be configured, for example, by forming a tapered shape on the outer diameter side of the stretched portion 11.

Further, in the present embodiment, the starting point (starting point) of the stretched portion 11 and the starting point of the slow-reduced diameter structure 11a coincide with each other, but the present invention is not limited to this. That is, a part of the stretched portion 11 stretched from the facing portion 10t on the intake port 101 side has an outer diameter Rt having the same size as the facing portion 10t, and has a gradual outer diameter m that is continuously reduced in diameter. A configuration may be provided in which a loose diameter structure 11a is provided. That is, the slow-reduced diameter structure 11a may be configured to be formed in at least a part of the stretched portion 11.

Further, in the present embodiment, the outer diameter Rs of the lower end portion (exhaust port 133 side) of the stretched portion 11 and the value of the gradual outer diameter m at the lowermost end portion (exhaust port 133 side) of the slow-reduced diameter structure 11a match. However, it is not limited to this. That is, the value of the gradual outer diameter m at the lowermost end portion of the slow-reduced diameter structure 11a and the value of the inner diameter r of the facing portion 10t may be the same.

The stretched portion 11 has a function of reducing the stress generated at the lower end of the cylindrical portion 102d, but from the viewpoint of stress reduction, by providing the reduced diameter portion 50 and the loosely reduced diameter structure 11a, the effect of further reducing the stress is achieved. There is.
Therefore, within the range of dimensional restrictions, the reduced diameter portion 50 and the stretched portion 11 due to the loosely reduced diameter structure 11a are provided.

FIG. 8 is a diagram showing a connection mode of the reduced diameter portion 50 with the slowly reduced diameter structure 11a.
Since stress is likely to be concentrated at the connection portion between the loosely reduced diameter structure 11a and the reduced diameter portion 50, it is preferable to have a structure in which stress concentration is unlikely to occur.
In FIG. 8A, a taper structure X is adopted for the slow-reduction diameter structure 11a. Also. In FIG. 8B, the corner R shape Y is adopted for the loose diameter structure 11a.
Even structures other than those shown in FIGS. 8A and 8B can be used in the present embodiment as long as they can reduce stress concentration.

In the present embodiment, the gradient of the slow-reduced diameter structure 11a is formed in a linear shape in the cross section, but the present invention is not limited to this. For example, although not shown, the gradient of the slow-reduced diameter structure 11a may be formed in a curved shape in a cross section.

With the above-described configuration, in the present embodiment, the stress applied to the inner diameter side of the slow-reduced diameter structure 11a, which is a portion caused by the creep life in the cylindrical portion 102d, is reduced without lowering the rotation speed of the rotating body including the cylindrical portion 102d. can do.
Further, since the creep phenomenon can be prevented without lowering the rotation speed, it is possible to prevent the exhaust performance of the turbo molecular pump 100 from being deteriorated by lowering the rotation speed.
Alternatively, since the rotation speed of the rotor portion including the cylindrical portion 102d can be increased by this configuration, the exhaust performance of the turbo molecular pump 100 can be improved.
The diameter-reduced portion 50 is described assuming that the outer diameter of the diameter-reduced portion 50 is constant in Rs, but the diameter is not limited to this, and the diameter may be further reduced toward the lower end.
Further, although the reduced diameter portion 50 and the slow-reduced diameter structure 11a have been described separately, the structure is such that both are integrated or each has a slow-reduced diameter structure in which the outer diameter gradually changes to the lower end. You may.

In addition, the embodiment of the present invention and each modification may be configured to be combined as necessary.

Further, the present invention can be modified in various ways as long as it does not deviate from the spirit of the present invention. And it is natural that the present invention extends to the modified one.

10t Opposing part 11 Extension part 11a Slow diameter structure 50 Reduced diameter part 100 Turbo molecular pump 101 Intake port 102 Rotor blade 102d Cylindrical part 103 Rotor shaft 123 Rotor shaft 123 Fixed wing 125 Fixed wing spacer 127 Outer cylinder 129 Base part 131 With screw Spacer 131a Thread groove 133 Exhaust port 200 Control device

Claims (5)

The exterior body on which the intake and exhaust ports are formed,
A thread groove type exhaust mechanism fixed to the exterior body and having a thread groove,
A rotating shaft contained in the outer body and rotatably supported,
It has a facing portion that is disposed on the rotating shaft and faces the threaded groove type exhaust mechanism via a gap, and a stretched portion that extends downstream from the threaded groove type exhaust mechanism, and the facing portion in the stretched portion. A reduced diameter portion having an outer diameter smaller than the outer diameter of the screw, and a rotating cylinder having a slow-reduced diameter structure that reduces stress concentration.
A vacuum pump characterized by being equipped with.
The vacuum pump according to claim 1, wherein the slow-reducing diameter structure is a tapered structure.
The vacuum pump according to claim 1, wherein the slow-reducing diameter structure has a curved surface shape.
The vacuum pump according to any one of claims 1 to 3, wherein the slow-reduced diameter structure is included in the reduced-diameter portion.
The exterior body on which the intake and exhaust ports are formed,
A thread groove type exhaust mechanism fixed to the exterior body and having a thread groove,
A rotating cylinder of a vacuum pump including a rotating shaft contained in the outer body and rotatably supported.
It has a facing portion that is disposed on the rotating shaft and faces the threaded groove type exhaust mechanism via a gap, and a stretched portion that extends downstream from the threaded groove type exhaust mechanism, and the facing portion in the stretched portion. A rotating cylinder characterized by having a reduced diameter portion having an outer diameter smaller than that of the outer diameter and a slow-reduced diameter structure for reducing stress concentration.

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